The Brown Recluse: How Dangerous Is It?

Cover Photo: © Andrew Hoffman, 2012, some rights reserved

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype.

Cover Photo: © Andrew Hoffman, 2012, Photo Library, some rights reserved.

By Dave Frank, Contributor

Recluse spiders are some of the most feared spiders in America. Rumors of infestations, highly dangerous bites, and even deaths have spread throughout the country. Yet despite the rampant arachnophobia, brown recluses are actually not so dangerous when we take a closer look at the spider behind the hype. Let’s explore some common myths and misconceptions about the brown recluse!

Myth #1: Recluse bites are extremely dangerous!

First, we need to address the rates of spider bites in general. There are many myths about spider bites. One common myth is that you can tell a spider bite from another bug bite, such as a mosquito bite, because a spider bite will have two puncture wounds while a mosquito bite will only have one. While it is true that spiders bite with two fangs, in contrast to the bite of a mosquito’s single mouthpart, spider fangs are usually too small and close together for us to actually see both bite marks. A spider bite would appear as a single wound, much like a mosquito bite. In fact, mosquitos are responsible for far more deaths worldwide than spiders.

According to Rainer Foelix’s Biology of Spiders, “only four genera are known to cause potentially deadly bites.” Loxosceles reclusa, the American brown recluse, is one of these spiders, but most recluse bites are harmless. The venom of spiders is used to paralyze their prey, so bites on humans would only be defensive. And this is a rare case, as recluses (as with most spiders) are not aggressive towards humans. They are actually much more scared of us than we are of them!

Their bites are necrotic, which means that their venom causes tissue degeneration at the site of the bite. This is different from spiders such as the black widow, Latrodectus mactans, which have neurotoxic venom. Neurotoxic venom will cause nerve damage and paralysis to prey. For humans, the bite of a recluse is very unlikely to lead to significant injury or death. We are much larger than their usual prey, so their bites do not contain enough venom to hurt us much. As long as one seeks medical attention for wounds causing pain or that won’t heal, recluse bites are survivable.

Myth #2: Brown recluses are common in California!

In America, the range of the brown recluse is contained mainly in the southern states. While there have been sightings in California, these are extremely rare. In fact, an entomologist at University of California, Riverside argues that there are no populations of brown recluses in California. Rick Vetter states that hundreds of spiders have been brought to the entomology department at UC Riverside for identification, and not a single one was a brown recluse.

Brown Reclue Range Map.gif
Recluse Range Map, taken from UC Riverside Entomology Department,

The map above shows the common ranges of recluse spiders in the U.S. Loxosceles reclusa is the species of brown recluse with bites that are the most medically significant. As you can see, their range does not extend west into California. While other recluse species can be found in California, these species do not have bites that are medically significant. Loxosceles deserta, the desert recluse, can be found in California, but they live far from urban areas and so are not considered dangerous due to their extremely limited interaction with humans.

Myth #3: Recluses are aggressive spiders!

As stated previously, recluses are not aggressive. There’s a reason they’re called “recluses” after all! Recluses like finding hidden spaces to build their nests. Older homes can be perfect habitats for them, but they often coexist peacefully with humans. As far as infestations go, there are many reports of recluses being found in large numbers. However, most of these events are blown out of proportion. In Brentwood, TN, a woman claimed to have been bitten several times due to an infestation in her apartment. However, the articles do not always have scientifically accurate information and may be misleading. For example, the main picture of “brown recluses” in this article does not show a brown recluse, as the spider shown is not even brown! While recluses can be found in high numbers in suitable locations, it is extremely rare for them to interact negatively with humans.

Myth #4: Brown recluses are difficult to tell apart from other spiders!

Brown recluses are quite easy to identify. The most telling feature of a recluse is the pattern of the eyes. Most spiders have eight eyes arranged in two rows. Recluses have only six eyes, and these are arranged in three pairs across the cephalothorax (head and torso region). They also have a violin shaped pattern along their backs, which is why they are sometimes called “fiddleback spiders”. Recluses are around ⅜ of an inch in length, a little smaller than a penny, and are have uniform brown coloration. Other spiders may have some of these aspects, but if a spider you are trying to identify does not have these characteristics, then you have not found a brown recluse.

Brown Recluse Spider
© Andrew Hoffman, 2012, Photo Library, some rights reserved

For those who may still be arachnophobic, please take a look at this video! This person is holding a brown recluse and a black widow, the most commonly feared spiders, in one hand. As you can see, neither spiders attack the cameraperson. These spiders are actually rather mild-mannered. We do not recommend trying this at home, but hopefully it shows that humans have very little to fear from our eight-legged friends.



Author: Taylor Crisologo

Taylor studied biology at Cornell University, where she worked with the Cornell Lab of Ornithology on projects ranging from breeding herring gulls off the coast of Maine to dancing lyrebirds in Australia’s Blue Mountains. When she’s not researching great places to experience Bay Area nature, you can find her birding or reading a book at home with her husband and their two indoor cats (Max and Penelope).

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